Winter Pests in Southern California

Friday December 19, 2014
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Wintertime Pests

Pests in California

Wintertime Pests in Southern California.

In Southern California, one of the ways you can tell its wintertime is when you see Californians remove their sunglasses! Otherwise, we natives (and those from afar) enjoy sunshine all year round, (wildlife and insects included). Winter in sunny Southern California is so mild that insects and wildlife enjoy not only the weather but the abundance of resources California has to offer, including our pantries. Plus, when the weather does turn cold and rainy (at least for California standards), insects and rodents are not shy about making your home their home during our short winter months.

Here are some of the critters that often become winter pests:


California has its own squirrel called; you guessed it, the “California Ground Squirrel.” In Southern
California Ground Squirrel

Ground squirrel tunnels make the landscape unstable.

California, breeding for ground squirrels begins around December. Ground squirrels make burrows that can easily be seen by the holes they leave behind. This can cause damage to the landscape making it unstable and risking injury when walking in the yard or mowing the lawn. Besides burrowing, ground squirrels love to eat vegetables or fruit from your trees, especially apples, peaches, and apricots. But, they don’t stop there; if no fruits or vegetables are available, ground squirrels will chew on bark and plastic sprinkler heads. They will also burrow around the roots of trees and plants. Squirrels are known to carry diseases, including bubonic plague, which can be transferred to humans by their fleas. Because breeding season is in the winter, squirrels are still very active in Southern California and continue to do damage to gardens and landscapes throughout the winter months.

Widow Spiders

Black widows are found throughout the United States but predominately in the southern and western states with frequent infestations in and around Southern California homes.
Female black widow

Female Black Widows are continues to be prevalent during Southern California’s winters.

The black widow tends to hide in dark corners, especially in the garage, and under wood piles. One would think widow spiders would go away come winter but because of our lovely weather, black and brown widows are prevalent year round
Black and Brown Widow Spiders

Brown and Black Widow Females – Note the spiky egg sac of the Brown Widow.

In late fall, brown widows are notorious for hiding underneath patio furniture, inside BBQ’s, and around playground equipment. The brown widow female is easily identified by her orange hourglass as well as the cream-colored spiky egg sac she’s usually protecting. Spiders have to be eliminated on contact, egg sacs and webs destroyed. Frequent sweeping and vacuuming is also necessary to keep them at bay. If you have a lot of spiders, it’s because you have a lot of insects – a spider’s food source.
Argentine Ants and Aphids

Argentine ants feeding on honeydew produced by aphids.

Argentine Ants

In California, there are ants in the summer, ants in the fall, ants in the winter, and ants in the spring. Southern California Residents often feel like they are living on one big gigantic ant hill; well they are, as are many Southern Californians. A huge, super colony of Argentine ants stretches along the coast of California and into nearby inland cities. In the heat of summer, ants are a constant nuisance appearing in droves and invading homes on a daily basis.Either they’re looking for water (and food, these ants prefer sweets) or in the winter, they’re running away from water when it starts to rain.

Not all ants are created equal …

An Argentine ant isn’t just any ant; one needs to know the kind of ant that is invading a home because for instance, eliminating Argentine worker ants doesn’t always get rid of an infestation.
Argentine Ant Nest

Argentine Ant Nest

Argentine ants have several queens in a colony, giving them the ability to make more worker ants to replace the ones that were eliminated.Queens will also split and start a new colony elsewhere. The nest must be found to actually eradicate a colony. This can be difficult if the ants are under the foundation of a home. After several attempts at home remedies, many homeowners find they need professional help in treating for Argentine ants. These ants will respond to organic pest management methods but depending on where one lives, a monthly or bi-monthly maintenance plan is usually necessary to control this particular ant species.

Rats and Mice

Rats and mice multiply very quickly; their urine and feces can cause health issues for you and your family. Just breathing in rodent urine and fecal matter through vents leads to diseases such as hantavirus pulmonary syndrome. It also can cause the lymphocytic choriomeningitis virus, which according to CDC (Center for Disease Control), “poses a particular risk for pregnant women.”
Roof rat

Roof rat helping himself to some grain.

Grease Rub

Dark, greasy-looking areas next to a hole or gap are called “grease rubs” – Evidence of rats going in and out of an access point.

Winter Rodent Activity

In the beginning of winter, there’s a lot more rat and mice activity; usually outdoors but if you have any broken screens, gaps, or holes in your roof, rodents this time of year will squeeze their way in and begin looking for nesting material to create a comfy home for their little ones. Rats and mice will also gnaw through food containers, stealing and contaminating as they make their way back to their nests. Regardless if you live in a 1200 square foot home or a 6000 square foot home or whether you are a great housekeeper (although it definitely helps if you keep food put away, sweep, and vacuum often) but if there are any, even little bitty openings, or doors left open, rodents will come indoors, especially in the winter – with their mother, their father, their brother, their sisters and all their cousins in tow.
California common snail

Did you know that the common garden snail in California was brought from France in the 1850’s as a source of food?

Rainy Day Snails

Snails tend to hide during hot weather and then become very active in the cool of winter, especially when it rains. (It is rather gross when the sidewalk is full of smushed snails during the rainy season). And in California, because of our mild weather, snails are active all year round.

Snail Resistant Plants

Pink Impatiens

Impatiens are one of the many flowering plants that resist snails.

Keeping snails at bay can be done naturally by planting snail resistant plants. These include geraniums, fuchsia, begonias, impatiens, and aromatic plants such as rosemary, sage, and lavender. If you have a garden with tomatoes, cabbage, lettuce, and the like, you’ll have to fend off snails daily. You can, however, remove as many hiding places from your garden and switch to a drip irrigation system instead of sprinklers. This prevents extra humidity and moisture in the garden and also in the landscape. Winter is here; the clouds are in the sky, sunglasses have come off (for the moment), the weather alternates between pouring rain and warm winter sunshine. Ants are coming and going. …This is Southern California. Article by Donna Walker


Mallis, Handbook of Pest Control, Tenth Edition, Saunders College Publishing, 2011 Imes, R. The Practical Entomologist, A Fireside Book, Simon & Schuster Inc., 1992. Print University of California Agricultural & Natural Resources, UC Riverside, IPM (Integrated Pest Management). Online Save Save Save Save Save Save Save Save Save Save Save Save Save Save


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